From: Mushfeq Khan <mushfeq.khan@...>
Date: 2007-03-12T08:41:18+09:00
Subject: Re: Metaprogramming and class_eval

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Hi,

You seem to have an extra .class in your modification to Class. You can get
away with this:

class Class
 def my_attr_accessor( *args )
    self.class_eval do
       attr_accessor *args
    end
 end
end

Explanation: When you're invoking my_attr_accessor from within the class def
of MyNewClass, 'self' is the class object MyNewClass (an instance of Class).
You need to call class_eval on this object. When the block passed into
class_eval is executed, 'self' is again the class object MyNewClass. This is
what allows you to access the private 'attr_accessor' method.

Mushfeq.

On 3/11/07, Pedro Del Gallego <pedro.delgallego@gmail.com> wrote:
>
> Hi
>
> Whats the differents between this three classes. Why the
> my_attr_accesor dosent create getters and setter clases.
>
>
> Thanks in advance
>
> #----------------------------------------------------------------------
> #
> #----------------------------------------------------------------------
>
> class Class
>   def my_attr_accessor( *args )
>      args.each do |name|
>        self.class.class_eval do
>           attr_accessor :"#{name}"
>        end
>      end
>   end
> end
> => nil
>
> class MyNewClass
>   my_attr_accessor :id, :diagram, :telegram
> end
> => [:id, :diagram, :telegram]
>
> class MyClass
>   attr_accessor    :id, :diagram, :telegram
> end
> => nil
>
> class Another_class
>   def initialize
>     ["id","diagram","telegram"].each do |name|
>        self.class.class_eval do
>           attr_accessor :"#{name}"
>        end
>      end
>   end
> end
> => nil
>
> mnc = MyNewClass.new
> => #<MyNewClass:0xb7b97d0c>
> mc  = MyClass.new
> => #<MyClass:0xb7b950fc>
> ac  = Another_class.new
> => #<Another_class:0xb7b82358>
>
> ac.diagram
> => nil
> mc.diagram
>
>
> --
> -------------------------------------
> Pedro Del Gallego
>
> Email              :   pedro.delgallego@gmail.com
>
>

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